Digital processing of electrical analog signals requires digitization of these analog signals, such that the analog signal is represented by a sequence of digital values. For that purpose the analog signal is sampled, for example, in a sample-and-hold circuit thus producing a sequence of discrete analog values. Subsequently the discrete analog values are quantized by an analog-to-digital converter, that is each analog value is mapped to one of a plurality of contiguous intervals, which is assigned to a digital number. In this way a value of the continuous analog signal is mapped to a discrete digital number. The digital value accordingly comprises an error except if the actual analog value exactly matches the middle of the interval to which it is mapped. This error is also known as quantization noise introduced by the step of quantization.
For digitizing an analog signal an analog-to-digital converter (ADC) can be used, wherein conventional ADCs may comprise a sample-and-hold sub-circuit. Linear ADCs, for example, linearly map an incoming signal to the range of output values. Typically the relative error of the output values is big for small amplitudes of the input signals and small for higher input amplitudes since small and big signal values are mapped to equally sized intervals. In contrast to that, conventional analog-to-digital converters comprising a non-linear quantization place more levels in ranges of small amplitudes, or more generally speaking in amplitude ranges of higher interest, and fewer levels where signal amplitudes are higher or less likely. However. these non-linear analog-to-digital circuits are comparatively complicated and thus expensive.